/**
 * Rate Limiter - Per-user and per-provider rate limiting with queuing.
 */
interface RateLimitConfig {
    maxRequests: number;
    windowMs: number;
}
export declare class RateLimiter {
    private userLimits;
    private providerLimits;
    private userConfig;
    private providerConfig;
    private maxQueueSize;
    constructor(opts?: {
        userLimit?: RateLimitConfig;
        providerLimit?: RateLimitConfig;
        maxQueueSize?: number;
    });
    /**
     * Check if a request is allowed. If not, queues it with backpressure.
     * Returns a promise that resolves when the request can proceed.
     */
    acquire(userId: string, provider: string): Promise<void>;
    private checkLimit;
    private processQueue;
    /**
     * Get current usage stats.
     */
    getUsage(userId?: string, provider?: string): {
        user?: {
            used: number;
            limit: number;
            windowMs: number;
        };
        provider?: {
            used: number;
            limit: number;
            windowMs: number;
        };
    };
    /**
     * Reset all limits.
     */
    reset(): void;
}
export {};
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